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// Copyright The gittuf Authors
// SPDX-License-Identifier: Apache-2.0
package gitinterface
import (
"context"
"errors"
"fmt"
"io"
"strings"
"github.com/gittuf/gittuf/internal/signerverifier/gpg"
"github.com/gittuf/gittuf/internal/signerverifier/sigstore"
"github.com/gittuf/gittuf/internal/signerverifier/ssh"
"github.com/go-git/go-git/v5/plumbing"
"github.com/go-git/go-git/v5/plumbing/object"
"github.com/go-git/go-git/v5/storage/memory"
"github.com/secure-systems-lab/go-securesystemslib/signerverifier"
)
var (
ErrTagAlreadyExists = errors.New("tag already exists")
)
// TagUsingSpecificKey creates a Git tag signed using the specified, PEM encoded
// SSH or GPG key. It is primarily intended for use with testing. As of now,
// gittuf is not expected to be used to create tags in developer workflows,
// though this may change with command compatibility.
func (r *Repository) TagUsingSpecificKey(target Hash, name, message string, signingKeyPEMBytes []byte) (Hash, error) {
gitConfig, err := r.GetGitConfig()
if err != nil {
return ZeroHash, err
}
goGitRepo, err := r.GetGoGitRepository()
if err != nil {
return ZeroHash, err
}
targetObj, err := goGitRepo.Object(plumbing.AnyObject, plumbing.NewHash(target.String()))
if err != nil {
return ZeroHash, err
}
if !strings.HasSuffix(message, "\n") {
message += "\n"
}
tag := &object.Tag{
Name: name,
Tagger: object.Signature{
Name: gitConfig["user.name"],
Email: gitConfig["user.email"],
When: r.clock.Now(),
},
Message: message,
TargetType: targetObj.Type(),
Target: targetObj.ID(),
}
tagContents, err := getTagBytesWithoutSignature(tag)
if err != nil {
return ZeroHash, err
}
signature, err := signGitObjectUsingKey(tagContents, signingKeyPEMBytes)
if err != nil {
return ZeroHash, err
}
tag.PGPSignature = signature
obj := goGitRepo.Storer.NewEncodedObject()
if err := tag.Encode(obj); err != nil {
return ZeroHash, err
}
tagID, err := goGitRepo.Storer.SetEncodedObject(obj)
if err != nil {
return ZeroHash, err
}
tagIDHash, err := NewHash(tagID.String())
if err != nil {
return ZeroHash, err
}
return tagIDHash, r.SetReference(TagReferenceName(name), tagIDHash)
}
// GetTagTarget returns the ID of the Git object a tag points to.
func (r *Repository) GetTagTarget(tagID Hash) (Hash, error) {
targetID, err := r.executor("rev-list", "-n", "1", tagID.String()).executeString()
if err != nil {
return ZeroHash, fmt.Errorf("unable to resolve tag's target ID: %w", err)
}
hash, err := NewHash(targetID)
if err != nil {
return ZeroHash, fmt.Errorf("invalid format for target ID: %w", err)
}
return hash, nil
}
// verifyTagSignature verifies a signature for the specified tag using the
// provided public key.
func (r *Repository) verifyTagSignature(ctx context.Context, tagID Hash, key *signerverifier.SSLibKey) error {
goGitRepo, err := r.GetGoGitRepository()
if err != nil {
return fmt.Errorf("error opening repository: %w", err)
}
tag, err := goGitRepo.TagObject(plumbing.NewHash(tagID.String()))
if err != nil {
return fmt.Errorf("unable to load commit object: %w", err)
}
switch key.KeyType {
case gpg.KeyType:
if _, err := tag.Verify(key.KeyVal.Public); err != nil {
return ErrIncorrectVerificationKey
}
return nil
case ssh.KeyType:
tagContents, err := getTagBytesWithoutSignature(tag)
if err != nil {
return errors.Join(ErrVerifyingSSHSignature, err)
}
tagSignature := []byte(tag.PGPSignature)
if err := verifySSHKeySignature(ctx, key, tagContents, tagSignature); err != nil {
return errors.Join(ErrIncorrectVerificationKey, err)
}
return nil
case sigstore.KeyType:
tagContents, err := getTagBytesWithoutSignature(tag)
if err != nil {
return errors.Join(ErrVerifyingSigstoreSignature, err)
}
tagSignature := []byte(tag.PGPSignature)
if err := verifyGitsignSignature(ctx, r, key, tagContents, tagSignature); err != nil {
return errors.Join(ErrIncorrectVerificationKey, err)
}
return nil
}
return ErrUnknownSigningMethod
}
func (r *Repository) ensureIsTag(tagID Hash) error {
objType, err := r.executor("cat-file", "-t", tagID.String()).executeString()
if err != nil {
return fmt.Errorf("unable to inspect if object is tag: %w", err)
} else if objType != "tag" {
return fmt.Errorf("requested Git ID '%s' is not a tag object", tagID.String())
}
return nil
}
func getTagBytesWithoutSignature(tag *object.Tag) ([]byte, error) {
tagEncoded := memory.NewStorage().NewEncodedObject()
if err := tag.EncodeWithoutSignature(tagEncoded); err != nil {
return nil, err
}
r, err := tagEncoded.Reader()
if err != nil {
return nil, err
}
return io.ReadAll(r)
}
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